228 Forestry Quarterly. 



A series of tests with differently shaped indenting pieces was 

 made, namely, with a cone, a wedge, and a cube. The interesting 

 results shown in a diagram reveal the fact that the indentations with 

 the wedge remain proportional to the pressure — a straight line, while 

 the curves of ball indentations after a certain pressure is reached 

 become convex, and of the cone concave, i. e., disproportionate to the 

 pressure, showing that other and different factors in the two cases 

 than hardness have exercised an influence.* With the cube in dry 

 coniferous wood a maximum resistance was soon found, as in the ball 

 curve, while with moist conifer and broad-leaved v/ood the curve of 

 the cone is imitated. 



Factors which influence hardness of wood are : 



( 1 ) Anatomical structure ; hence character of annual ring, its 

 width, heartwood and sapwood and the face, tangential, radial or 

 cross-section, vary; (2) Specific weight; (3) Moisture per cent. 



The hardness of the cross section was found to be in conifers 30 

 per cent., in deciduous wood 20 per cent., less than that of the arith- 

 metic means of the two length sections (radial and tangential). This 

 is an opposite result to that of Biisgen's, the difference being due to 

 the indenting piece, a pin. 



Generally speaking, the relation of specific weight and hardness 

 is the same as in other exhibitions of strength; at least in the same 

 species the heavier is the harder wood, though not from species to 

 species; similarly, the increase of summerwood per cent, increases 

 hardness. In conifer wood, the more definitely bounded, the darker, 

 and the broader the summer wood, the greater the weight, and hence 

 strength and hardness. The same holds good in broad-leaved trees. 

 In these the colored heartwood shows increased hardness, but the in- 

 creased resin contents of the conifer heartwood has the opposite ef- 

 fect, as with other exhibitions of strength, is experienced with mois- 

 ture additions. Wet wood is about half as bard as dry wood; the 

 coniferous wood especially loses hardness by wetting. Surprisingly, 



*[It is a pity that, like Biisgen, the author overlooked or ignored 

 the work of Mr. Sharpies for the Tenth Census on American woods, 

 which was carried on with a wedge-shaped, dull, indenting piece. 

 This design appears to us still superior to the ball in the case of such 

 a non-homogeneous body as wood, because it averages up soft and 

 hard tissues better, and comes nearer to imitating the majority of 

 practical tests of hardness ; indeed, the author's tests seem to show 

 this, since the indentations with his wedge remained continuously 

 proportional to the pressure. — Ed.] 



